Other artificially propagated sorts of fungi which are used in a similar way against other types of weeds, are known (see Weed Science 21 (1973), 303 et seq., Ann.Rev. Phytopathol. 17 (1979), 301 et seq., and Plant Disease Reporter 58 (1974), 355 et seq.) and these so-called mycoherbicides are sold to-day under the trademarks Devine.TM. and Collego.TM. (Phytopathology 73 (1983), 774).
As of the date hereof, weeds belonging to the Compositae are controlled with chemical herbicides. These often have little effect on the weeds, which fact may be due to unfavourable climatic conditions at the time of spraying or to the fact that use of the known herbicides over an extended period of time selects for herbicide tolerant types of weeds. For these reasons and for environmental reasons it is desirable to use biological herbicides.
The fungus Phomopsis cirsii Grove was described for the first time by Grove in British Stem- and Leaf-fungi (Coelomycetes) 1 (1935), 177, and the fungus Septoria cirsii Niessl was described by Saccardo in Sylloge Fungorum 3 (1884), 550.
The pathogenic effects of Phomopsis cirsii and of Septoria cirsii on plants have so far been unknown. Surprisingly, it has now been found that Phomopsis cirsii attacks the leaf veins and stems of the host plants which as the disease progresses will shrink and wither. Such symptoms can be traced to the formation of toxins in the plant. The secretion of specific phytotoxic substances from the fungus or from interaction between the plant and fungus can also be seen in that parts of the infected plant, which show no signs of invasion by the fungus, turn yellow and wither earlier than they would normally have done. This means that phytotoxic products elaborated by the fungus have a controlling effect on the host plants.